This invention relates to metal cleaning compositions in general, and particularly to chrome cleaning compositions and methods or processes for cleaning metal, especially chrome and stainless steel.
Chromium forms an oxide layer on its surface when it is exposed to air. The oxide layer is not visible and thus chrome plated surfaces remain bright for some time. More importantly, the oxide layer, unlike iron oxide (rust) is not porous. Thus the oxidized layer prevents corrosive materials from penetrating to the chromium or other metals beneath the oxide layer, protecting those materials from further oxidation. The chromium content in stainless steel provides the same protection against corrosion in that alloy.
Chrome plated surfaces do, however, become contaminated. Particularly items such as bathroom fixtures get contaminated with a scale of metal salts, such as calcium and magnesium carbonate. In addition, the protective chromium oxide layer may be physically broken or pitted, allowing underlying metals to oxidize and corrode.
Conventional chrome cleaning processes have generally used abrasive materials and high pH (alkaline) conditions to clean such contamination. Such cleaners typically are in a liquid, gel or cream form, and may include a wax which can be buffed after cleaning as further protection.
It has been known that a silicate bond on the surface of a metal will provide additional protection. Such a coating may provide a ceramic-like protection against alkali, acid and contamination. The silicate bonding processes of the prior art typically include rigorous environmental conditions, such as exposing the surface to heat and alkali, often under an inert atmosphere.